Operating a pressurized reactor such as a fluidized bed coal gasifier or combustor involves discharging fine particles under high pressure and temperatures to storage bins under atmospheric pressure and low temperature (i.e., below 350° F.). The most commonly used method in such systems is a combination of a lock vessel and a screw cooler system. The screw cooler receives solids under high pressure and temperature and cools the solids by contacting them with the screw and the inner surface of the container.
In this conventional system, the lock vessel typically is a pressure swing vessel and has inlet and outlet valves. The lock vessel receives the cooled solids under pressure from the screw cooler through a normally open inlet valve. When the predetermined amount of solids enters the lock vessel, the inlet valve is closed and the vessel is subsequently depressurized to almost atmospheric pressure. The bottom discharge valve is then opened to discharge the solids to an atmospheric vessel. The solids in the atmospheric vessel can be disposed to proper storage vessels.
However, there are numerous disadvantages to the conventional system. One inherent disadvantage of this system is the number of moving parts which need to cycle often and operate in a synchronous manner. A second disadvantage is the difficulty in sealing the two ends of the shaft of the screw when the shaft is rotating under high pressure. Additionally, there are number of valves around the lock vessel, and the reliability of these valves can be less than desired because during each cycle, the valves must open and close in dusty environment. In normal operating conditions, the valves selectively are opened and closed millions of times under high pressure with a rapid flow of solid particles, thereby eroding the valves. Thus, conventional commercially available systems can have availabilities on average of less than 70%.
What is needed then is a system for cooling and continuously depressurizing the fine particles without the inherent issues mentioned above.